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PARKINSON, MURPHY, SHARED CONTINGENCY 91

method soon found that out. If we concentrated entirely on maintaining float (or
slack) in the critical path, eventually enough work that was not on the critical path
became critical, and the ability to accommodate slippage anywhere in the project
had disappeared. If using the CCPM method, a similar danger exists if we put all
of our eggs in one basket, by just concentrating on the critical chain.

I prefer to supplement the traditional critical path analysis with something that
I call Accomplishment Value.

Using Accomplishment Value to Supplement Float Analysis

Accomplishment Value, or Earned Value (a.k.a. Budgeted Cost of Work Per-
formed) pertains to the measurement of accomplishment against the plan, once
the work is underway. It is quite easy and practical to employ just part of the
earned value protocol, for measuring the rate of work accomplishment against the
plan. To use the EV approach, identify your tasks, assign a cost (or other weight
factor) to each task, and schedule all tasks (either manually or by CPM). The
computer will calculate the BCWS or Planned Accomplishment for any point of
time, by multiplying the planned percent complete of each task by the value
(cost) of the task. Now, when it comes time to progress the schedule, just enter
the percent complete of any tasks that have started. The system will multiply the
percent complete by the budgeted cost, producing the earned value. This gives us
a weighted measure of accomplishment, which can be compared to the planned
accomplishment. If the earned value (BCWP) is less than the planned accom-
plishment (BCWS), work is not being accomplished as fast as planned, and you
can say that the project is behind schedule.

Interestingly, some of the CCPM advocates knock the EVA methods, claiming
that they do not tell an accurate story due to a basis on cost rather than duration.
This is not necessarily correct. For a more detailed explanation of Earned Value
Analysis, see Section 8.

Parkinson, Murphy, and Shared Contingency

A common thread among all the commentary on shared contingency methods is
that we must defend ourselves from Parkinson’s Law. It was C. Northcote Parkin-
son who said “Work expands so as to fill the time available for that work.” If we
mask the contingency from the real estimate, we tend to realize a self-prophecy that
will use the entire duration that was applied to the task (including the contingency).
By pulling the contingency out of the task and grouping it with other contingency in
the path, we retain the shorter (and achievable) task duration as a target.

Being subject to Murphy’s Law as well as Parkinson’s Law, we obviously have to